Spectre Attacks: Exploiting Speculative Execution

TL;DR

Spectre attacks exploit speculative execution in modern CPUs to leak sensitive information through side channels, challenging many existing security assumptions and requiring hardware and software redesigns.

Contribution

This paper demonstrates practical Spectre attacks that breach confidentiality by exploiting speculative execution, revealing vulnerabilities in widely used microprocessors and security mechanisms.

Findings

Spectre attacks can read arbitrary memory from victim processes.

Speculative execution violates security assumptions of OS, JIT, and container security.

Vulnerable CPUs are present in billions of devices from major manufacturers.

Abstract

Modern processors use branch prediction and speculative execution to maximize performance. For example, if the destination of a branch depends on a memory value that is in the process of being read, CPUs will try guess the destination and attempt to execute ahead. When the memory value finally arrives, the CPU either discards or commits the speculative computation. Speculative logic is unfaithful in how it executes, can access to the victim's memory and registers, and can perform operations with measurable side effects. Spectre attacks involve inducing a victim to speculatively perform operations that would not occur during correct program execution and which leak the victim's confidential information via a side channel to the adversary. This paper describes practical attacks that combine methodology from side channel attacks, fault attacks, and return-oriented programming that can read arbitrary memory from the victim's process. More broadly, the paper shows that speculative execution implementations violate the security assumptions underpinning numerous software security mechanisms, including operating system process separation, static analysis, containerization, just-in-time (JIT) compilation, and countermeasures to cache timing/side-channel attacks. These attacks represent a serious threat to actual systems, since vulnerable speculative execution capabilities are found in microprocessors from Intel, AMD, and ARM that are used in billions of devices. While makeshift processor-specific countermeasures are possible in some cases, sound solutions will require fixes to processor designs as well as updates to instruction set architectures (ISAs) to give hardware architects and software developers a common understanding as to what computation state CPU implementations are (and are not) permitted to leak.